This invention relates to a precombustion chamber construction for a diesel engine, and more particularly a precombustion chamber provided with a glow-plug in a side wall of a ceramic precombustion chamber.
Ceramic precombustion chambers superior in heat-resistant and thermal insulating properties have been practically used for diesel engines. A construction of a ceramic precombustion chamber provided with a glow-plug has been disclosed in Japanese Utility Model Application Publication No. 61-18,188 as shown in FIG. 1.
The known construction shown in FIG. 1 comprises thermal insulating spaces 3 in a side wall 7 of the ceramic precombustion chamber 4 and a glow-plug receiving aperture 10 formed in a glow-plug guide 14 of the side wall 7 and communicating with a glow-plug mounting threaded aperture 13 in a metal cylinder head 2.
In such a precombustion chamber for an internal combustion engine, the glow-plug is often provided on a side of a side wall of the ceramic precombustion chamber by reason of design. In this case, however, there is a clearance between the glow-plug and the glow plug receiving aperture, through which burned gases leak into the thermal insulating space to lower the thermal insulating effect. Moreover, actual compression ratios of the engine are changed to interfere with normal engine performance.